At present chip producers in the semi-conductor industry are working on the introduction of so-called 65-nanometer structures (Computertechnik (10), 2007). Even smaller structures of 45 nm are in the process of being developed. However, these dimensions too are only intermediate steps on the road to even smaller structures. Based on the advancing miniaturisation of semi-conductor components, new challenges are arising for the manufacturers of printed circuit boards with chip-carriers to adapt their products to new conditions. This means, for example, that current demands for structure dimensions of approx. 25 μm have to be realised if they want to stay in the market. At the same time, it is already clear that in the near future dimensions will get even smaller. It is no longer possible to realise such precision structures with the necessary quality using today's conventional methods and apparatuses in printed circuit board production. In the miniaturisation of structures, structures with irregular contours, even bridges (short-circuits) or interrupts are considered. In addition, it has also been established that the uniformity of the metal layers deposited is insufficient. This is not acceptable as the electric characteristics of the circuits produced in this way will be impaired in an unforeseeable manner, which means that the circuits will have to be thrown away.
The aforementioned requirements for the highly precise production of printed circuit boards come with demands to be able to produce these printed circuit boards again and again in very large quantities in as cost-effective manner as possible.
It is of particular significance, more especially for the production of very precise structures with the aforementioned dimensions, to be able to create the metal layers required for this with as uniform a layer thickness as possible. If not, non uniform structure profiles (widths, flanks, heights) are formed setting limits to miniaturisation.
For the wet chemical treatment of work pieces, for instance for metallization or for etching, the work pieces are brought into contact with a treatment fluid, for example by immersion into a container containing the treatment fluid or by conducting a jet of the treatment fluid onto the surface of the work piece. In doing so, the work pieces can be guided through a treatment system in a batch-wise manner or also by means of a continuous conveyor on which they are treated. During the treatment, the work pieces can be retained in an upright position or in a horizontal position. The latter is applicable in particular to plates in continuous transport. Printed circuit boards, for example, are typically treated either in dip tanks in the upright position or in a continuous conveyorized system in which the work pieces are held in the horizontal position and are continuously conveyed (for example WO 98/374 A2). In the latter case, the treatment fluid can be kept, for example, in a stationary bath, the work pieces being guided through the said bath.
For electrodeposition, it is typically advantageous to set the treatment fluid used for the metal deposition in motion for example by blowing in air, so that a sufficient fluid exchange takes place at the surface of the work pieces to be treated and more especially in small holes in the work pieces. In addition, nozzles can also be provided, for example, for conducting treatment fluid to the work piece surfaces, with their nozzle openings below the level of the fluid.
For example U.S. Pat. No. 4,622,917 discloses an apparatus for electroless metal plating, where a printed circuit board is retained in the upright position in a bath container and, in doing so, is immersed into a treatment fluid. Fluid distributors are disposed on both sides of the printed circuit board, the said fluid distributors being separated from a treatment region by defining walls, which face the printed circuit board and include a plurality of holes, the printed circuit board being situated in the said treatment region. The printed circuit board is moved back and forth during the treatment at right angles to the fluid flow generated by the holes. The fluid distributors are used in an alternating manner for incoming flow with the fluid and for removal by suction, one fluid distributor being for the incoming flow of fluid to one side of the printed circuit board, whilst the other fluid distributor sucks out fluid at the same time from the other side of the printed circuit board. Consequently the fluid flows in an alternating manner into the one or into the other direction. This method of operation is to achieve both a uniform coating of the surface of the work piece and also of the hole walls in the printed circuit board.
In addition, DE 41 33 561 A1 describes an apparatus for electroplating for the improved treatment of the surfaces of printed circuit boards. In this apparatus a plurality of product items are secured to a product carrier in the upright position. During the treatment the products are subjected to either a vertical, linear up and down movement in an electroplating bath and at the same time a horizontal, circular movement or a vertical, circular movement and at the same time a horizontal, linear movement or a vertical, circular movement and at the same time a horizontal, circular movement. In particular, this is to eliminate air bubbles or gas bubbles forming as reaction products.
DE 43 22 378 A1, in addition, specifies a device for the surface treatment of printed circuit boards, where the boards are conveyed in the horizontal operating position and, in doing so, are treated. The board carries out a combination movement, which is composed from two autonomous relative movements that are independent of one another with respect to a treatment solution, wherein the board executes a first sliding continuous movement in a longitudinally extending path in one transport direction in a horizontal plane and, simultaneously with this, a second movement, which comprises powerfully pulsating vibration oscillations in rapid succession. These vibration oscillations can be in the plane of the board. This device is to strengthen the diffusion of the fluid situated in bores and in the vicinity of said bores, and consequently provides for considerable acceleration of the transport of the material to the boundary layer.
The named measures for moving the fluid have various disadvantages, the most important of which being that the fluid movement does not have the desired effectiveness with regard to the necessary uniformity of the effect of the treatment, both as regards time and also at least partially as regards location. Above all, the documents mentioned gave no reference to a uniform electrolytic treatment.